Ugandans voted on Thursday on the fate of President Yoweri Museveni, who is hoping for a fifth term after ruling the nation for the last 30 years.
The day began with many politically-minded voters unable to tweet or update their Facebook pages after a government ban on social media.
After casting his vote at his home in western Uganda, Museveni defended the ban as a "security measure to avert lies ... intended to incite violence and illegal declaration of election results."
Human rights groups condemned the social media clampdown. Many citizens accessed social media sites via encrypted private networks. A similar shutdown occurred during the 2011 general election.
"The Ugandan government's decision to block access to social media on mobile phones on election day is a blatant violation of Ugandans' fundamental rights to freedom of expression and to seek and receive information," said Sarah Jackson, Amnesty International's deputy regional director. "Without clearly defined security concerns, this closure is nothing but an exercise in censorship as Ugandans elect their leaders."
Opposition candidate briefly held
Throughout the election, social media has been used as a rallying and debate tool.
In January, Ugandans used the hashtag #1986pictures
with tweets of 30-year-old pictures and remarks like "In 30 years, everything has changed in Uganda except the president."
Further complicating the vote, opposition candidate Kizza Besigye was detained in the area of Kasangati near the capital, Kampala, on Thursday, local police told CNN.
Besigye, who was released after about three hours, was detained after attempting to enter a call center he suspected was being used to store illegal election materials, Kampala police spokesman Patrick Onyango said.
Accompanied by journalists and members of a European Union observer mission, Besigye arrived at the secure police facility and demanded to be let in, Onyango said. Besigye has been arrested on numerous occasions in his bid for the presidency.
The mayor of Kampala, Erias Lukwago, was arrested in his home in the area of Rubaga, police said. The reason for the arrest is unclear.
The start of the election was delayed in in some polling stations because of what the electoral commission said was a shortage of election materials. The Commonwealth observer mission's leader, former Nigerian President Olusegun Obasanjo, called the delays "inexcusable."
Polls closed at 6 a.m. ET, with results expected Friday.
Uganda's Electoral Commission reported that a candidate of the ruling National Resistance Movement was arrested for ballot stuffing in the Busiro South constituency south of Kampala. The ballots stuffed in various boxes had votes for him and Museveni, the commission reported.
In the lead-up to the election, rights groups have warned that freedom of association and expression have been under threat.
"Uganda has seen increased levels of authoritarianism in the last decade," said Magnus Taylor, Horn of Africa analyst at International Crisis Group. "This has come in waves, most evident during election period when a generally strident opposition has clashed against the president's anti-democratic tendencies."
Few expect new leader to emerge
A crowd at one polling station in Kampala surged at a man they say had marked ballots in favor of Museveni. Police and military used tear gas a